The present invention relates to a process and apparatus useful in mounting and/or bonding semiconductor components to substrates and parts therefor.
A reflow (i.e., soldering) process is used to bond dies to substrates. A typical reflow process is performed after each die is placed onto a substrate. More particularly, after each die is placed onto the substrate by a bonding head, the bonding head heats the die so as to solder the die to the substrate. This heating step is repeated for each die, thereby making the overall die-substrate assembling process time-consuming and inefficient. Alternatively, a single heating process can be performed subsequent to the placement of a plurality of dies onto a set of substrates. More particularly, after a die mounting machine places the dies onto the substrates, the die and substrate assemblies are transported from the mounting machine to an external reflow oven/furnace by a separate moving mechanism, such as a conveyor system. While being transported to the external reflow oven/furnace, the dies and substrates may move relative to one another and may hence cause die/substrate misalignment.
In soldering dies to substrates, flux has been used, for instance, to temporarily secure the dies to the substrates. Various problems have been identified in connection with soldering processes using flux. For instance, optoelectronic devices are sensitive to flux residues due to absorption and bending of optical signals. As a result, a fluxless soldering process has been used in manufacturing die/substrate assemblies. Fluxless soldering has also gained increasing importance in recent years due to concerns for the environmental effect of common agents for cleaning flux residues, such as chlorofluorocarbons. Because fluxless soldering processes are typically performed at a relatively high temperature, solders are prone to oxidation, which is detrimental to die/substrate assemblies. Various attempts at fluxless soldering have been made with limited success.
Vacuum substrate chuck arrays have also been developed for holding substrates in place during die/substrate assembly. With reference to FIGS. 9A and 9B, substrates 820 are held in openings 852 formed in a vacuum substrate chuck array 850 by way of suction applied thereto through vacuum openings 858. Typically, the openings 852 are formed with round lower corners 854, preventing the substrates 820 from lying flat against the bottom 856 of the openings 852. As a result, the application of suction to the substrates 820 through the vacuum openings 858 is rendered inefficient and/or ineffective.
As discussed above, conventional die/substrate assembly processes and apparatus suffer from various problems and shortcomings. Accordingly, there is a need for an improved process and apparatus addressing such problems and shortcomings.
The present invention overcomes the disadvantages and shortcomings of the prior art discussed above by providing a new and improved die bonding apparatus and method and parts therefor. In accordance with one feature of the present invention, the apparatus includes a support frame and a placing mechanism mounted on the frame for placing a semiconductor component on a substrate. A reflow oven or furnace is mounted directly on the frame adjacent to the placing mechanism for heating a plurality of substrates and semiconductor components placed thereon in a substantially single operation directly on the frame, thereby eliminating the need to transport the semiconductor components and substrates to an external furnace.
A method for mounting semiconductor components to substrates is also provided. In accordance with this method, each of the semiconductor components is placed on a corresponding one of the substrate at a placing station, which is positioned on a support frame. The substrates and semiconductor components are then heated at a heating station. The heating station has an oven mounted directly on the frame adjacent to the placing station for performing the heating step directly on the frame. The substrates can be positioned on a supporting surface movably mounted on the frame prior to the performance of the placing step. The substrates can be positioned on the surface until the completion of the heating step.
In accordance with another feature of the present invention, a device for carrying a plurality of substrates includes at least one plate having a plurality of openings, each of which is sized and shaped so as to receive a substrate. Each of the openings is defined by a side wall and a bottom wall. Each of the bottom walls has a mechanism for applying suction to a substrate received in a corresponding one of the openings. Each of the side walls cooperates with a corresponding one of the bottom walls so as to form a substantially sharp corner such that a substrate can lie substantially flat against a corresponding one of the bottom walls. The plate can be provided with first and second plates attached to each other. In such circumstances, the openings can be formed in the first plate, extending completely through the first plate. The side walls are defined by the first plate, while the bottom walls are defined by the second plate. Each of the side walls and bottom walls are substantially straight.
Another feature of the present invention involves a mounting method including the steps of positioning a substrate and a semiconductor component placed on the substrate in a substantially air-tight compartment and withdrawing air contained in the compartment. The substrate and the semiconductor component have an eutectic solder positioned therebetween. The compartment is heated by supplying a heated gas into the compartment for a predetermined period of time so as to reflow the eutectic solder positioned between the substrate and the semiconductor component. The heated gas is substantially free of oxygen so as to inhibit oxidation of the solder. In this manner, a fluxless soldering can be performed.